By Rania Gollakner, BS, DVM, MPH

What is dextromethorphan?

Dextromethorphan (brand names: Delsym®, Robitussin®, Balminil®, Benylin ® and many others) is a medication used to treat compulsive behavior. It can also be used as a cough suppressant, although other cough suppressants are typically more effective in cats and dogs.

Its use in cats, dogs, and horses to treat compulsive behavior or cough is ‘off label’ or ‘extra label’. Many drugs are commonly prescribed for off label use in veterinary medicine. In these instances, follow your veterinarian’s directions and cautions very carefully as their directions may be significantly different from those on the label.

How is dextromethorphan given?

Dextromethorphan is given by mouth in the form of a tablet, gelcap, or liquid. It is also available in other forms, but these are more difficult to administer to pets. It may be given with or without food; however, if your pet vomits when given this medication on an empty stomach, give future doses with food or a treat. Measure liquid forms of this medication carefully. This medication will take effect quickly, in about 1 to 2 hours, and improvement in clinical signs should follow.

What if I miss giving my pet the medication?

If you miss a dose, skip the dose you missed and give it at the next scheduled time, and return to the regular dosing schedule. Never give your pet two doses at once or give extra doses.

Are there any potential side effects?

Side effects are uncommon, but may include vomiting, diarrhea, decreased appetite, sleepiness, drooling, or anxiousness. More serious side effects include rapid heartbeat, collapse, muscle tension, incoordination, muscle twitches, seizures, and abnormal eye movements.

This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.

Are there any risk factors for this medication?

Dextromethorphan should not be used in pets that are allergic to it. It should be used cautiously in pets with liver disease, skin allergies (atopy), chronic cough, or wet coughs. Dextromethorphan should be used cautiously in pets that are taking MAOIs, or have recently used products such as amitraz containing collars or selegiline. While it is considered safe in pregnant humans, use cautiously in pregnant or lactating pets as the safety has not been established.

Are there any drug interactions I should be aware of?

The following medications should be used with caution when given with dextromethorphan: CYP2D6 inhibitors, metoclopramide, MAOIs, naloxone, opioids, quinidine, serotonergic agents, or tramadol.

Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking.

Is there any monitoring that needs to be done with this medication?

There is no specific monitoring that needs to be done while your pet is taking this medication. Your veterinarian may monitor your pet to be sure that the medication is working. Monitor your pet at home for serious side effects.

How do I store dextromethorphan?

Store at room temperature between 68°F and 77°F (20°C and 25°C) and protected from moisture.

What should I do in case of emergency?

If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility.

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